Cannot login to Ubuntu, Pkexec and sudo isn't working

Question

I am completely new to Linux and I just realize that what I have done is extremely screwed up.

I was run around finding a way to get some installing package on my machine to work out. Unfortunately, I have screwed up really bad by modify the permission in /usr to all files and folders and also, the sudoers.o file.

Then I used pkexec to set all the permission of my /usr to 755. Luckily now I can access to my terminal but the sudo,pkexec,apt-get command is not working at all and I still not be able to enter Ubuntu.

Is there a way to fix this, (or getting my file from the system to keep it in my external hdd without installing anything so that I can start do my clean install again?)

Answer 1

if the disk its not encrypted, then use some usb live , here you can get a guide. how to make usb live on windows and mac os how to make usb live on ubuntu

boot your new live system open a terminal

get root by using sudo bash command

try to get the device name and the file-system with the fdisk -l (example /dev/sdb1)

create a folder to mount the disk over /media/ folder mkdir /media/hdd

mount the disk mount -t ext4 /dev/sdb1 /media/hdd

mount the disk where you want to store your files with the same procedure

if you just want to copy them use cp -t /path/toThe/files /path/toThe/storeFolder/

if you want to compress them i use use tar and gz by the

tar -cvzf file.tar.gz /path/toThe/homeUser 

but i let you a more detailed guide of tar opcions to figure figure out witch option work better for you tar guide